You can blacklist them (lighting bolt icon at end of game screen). If you think the exchange crossed the line to harassment, you can send me a personal message (click my name left in this post and then on the left side, under "Actions", should be an entry "Send personal message."

Behind a gamer a % are needed where you can see how may games this player finished when he lost. Only for games with 3 or more players. If he win 10 and lost 5 and resign one of the 5 before end, then 80% must be shown behind the player name. Then it must be possible that I can enter a % value how many % a player must have that I play with him. Already written above ... not needed for 1vs1 games.